Collapsible named groups for Installed Mods list

[Doc0160]

My issue trying to find a mod from a long list of downloaded mods.
It's easier to find a mod from a grouping you made and named yourself than trying to remember the name of a specific mod.
It has also the benefit of being able to check if a submod is in your current load order or not very easily, depending on how you make your groups.

Idea from groups in #603, collapse in #369, and separators from Mod Organizer 2.

Screenshot of the feature from Mod Organizer in its equivalent for the "Installed Mods" panel :

In Mod Organizer, this feature can be described as a separator with added collapsible features or even a virtual mod with special UI handling.
One of the limitations of their system is that you can't collapse mods under it if the list isn't sorted by priority (because it is sorted like every other mod).
But it removes the complexity of more formal group implementations data-wise by keeping it a list instead of nested values.
Priority being both the user specified order in the Installed Mods list and the default position relative to other mods when added to the Collection Mods list for Mod Organizer.
(And sorting in Mod Organizer and doesn't change the Order/Priority column, so actual order is always preserved.)

But I don't think there is a clear winner for the user between collapsible separators or actual groups in the end.

[bcssov]

After reviewing the request and current UI architecture, this will likely move toward expanding the existing filter/query system rather than introducing full nested groups or MO2-style separators.

Paradox descriptors already expose tags/categories metadata, for example:

tags={
    "Species"
}

The likely direction is adding tag/category filtering support to the existing query engine:

tags:species
tags:graphics&&selected:yes
tags:species||ui
tags:--music

This avoids breaking the current flat ordering model while still improving large mod list organization and discoverability.

Lightweight visual separators may still happen later, but not as true nested groups for now.

Marking as vnext while this direction is evaluated further.

[SmaugTD]

Just for inspiration I think I like the way that Warhammer 3 Mod Manager does it the best. There is a separate UI tab for category view where mods can be given category tags, and are then sorted automatically into multiple categories based on the tags. Existing tags can be added from a dropdown search menu.
I don't much trust Paradox and mod creators to always have useful categories and it could be useful to sort mods based on compatibility with other mods or game version support.

[Doc0160]

With the filter, a column with tags coalesced would be useful visually "Species, UI, Gra..."
It's better discoverability without filters and provide examples of values to use in the filter.

Some mod managers do a full featured tag list instead of coalesced text that column to provide more options : each tag is a sub-element in the column, and filtering by that tag can be done by clicking on it, or opening the tag's "..." dropdown for options, or right click for options, etc.
But this is usually paired with being able to add and remove user-defined tags to mods, so not as useful with mod-defined tags.

(An easier way to use filters, without needing the wiki open, or needing to memorize, would be nice too. #389, or suggestion/auto-complete as you type. But that is a separate issue.)

A big issue with mod-defined tags is that they aren't filled reliably by mod authors.
Ex: UI not being tagged as UI because it's not on the list of pre-defined tags, so mod authors use whatever tags seems good to therm, with no consistency between mods. (And some mod authors don't bother with tags at all.)
Editing mod-defined tags in local mods for better filtering would be an option, but it's more complicated for downloaded mods (source steam or paradox).
A "decide yourself" option would be better (custom tags, separators, groups, etc.).

To be clear : I'm 100% in favor for filters based on mod-defined tags.
But it' a lot less useful at solving the issue than user controlled solutions.

Edit : @SmaugTD, glad to know that I'm not the only one noting the issue with mod-defined tags.

I'm going to extend that with Stellaris as an example : official tag filters are bad. You can't easily search for mods using useful tags, so why would mod authors bother using them in their mod ?
Paradox Mods has a limited list of tags you can filter by, and there has been some issues uploading mods with tags outside of that list.
Steam doesn't have the issue with uploading, but doesn't provide an easy way to filter by tags : the list of tags on the search page is the same as Paradox Mods. On the mod page you can click on tags to search for other mods with that tag, including tags outside the list, otherwise you have to fiddle with the URL for useful tag filtering.
The pre-defined list doesn't have tags UI, Traditions, Music, AI, Ascension, and other things you would like to filter by either.