Add some user defined placeholders to firmware and Bambu Studio

[julie777]

Is your feature request related to a problem? Please describe.

I currently have multiple profiles defined for the same printer/nozzle size. This is a problem because changing profile also changes filament and process and sometimes I do not notice those changes. In addition, It requires re-slicing the plate before printing.

Describe the solution you'd like

Having a single printer model/nozzle size profile is the ideal situation.
Currently that allows choosing to capture timelapse or run the bed level calibration as print time options so those do not require a different profile. That also does not require re-slicing.

There are other print time decisions that a user might want.
I would like to have some user-defined placeholders defined so that a user can add custom print time configuration. I would suggest adding five of them - user1 through user5, which allows each user to use them for any desired purpose.

Here are some examples of what they might be used for:

• enabling some kind of function that will be taken by the expansion board (there might be multiple of these.)
• auto eject (I have have a profile that does not print a nozzle load line, and it waits after the print is complete until the bed has cooled sufficiently to release the part at which time it uses the print head to gently push the object of of the bed.
• skip all of the filament purging that happens with the default printer profiles provided.

Because the placeholders might be used for different purposes, they should be numeric values with true and false represented as 1 and 0.

Implementation

Add support by the firmware to evaluate user-defined placeholders.
Add support to Bambu Studio and firmware to communicate these placeholders as part of the print start.
For the Bambu Studio UI

• add placeholder definition to preferences so that placeholders in the user interface can have user defined names and types (boolean, integer)
• add the user defined placeholders which are defined in preferences to the print start dialog as either checkboxes or number entry text boxes based on the defined type.

Notes:

By requiring the user to define these placeholders in preferences, only users that want to use them will see them on the print dialog. This will prevent confusing novice users.

Having the actual name in the g-code be user1..user5 is not an issue as the advanced user can easily correlate the values. This prevents either having to transmit the mapping of names to firmware and handling it there, or having Bambu Studio translate the names in the custom g-code before sending to the printer.