QGIS plugin. This plugin enables a layer menu in a nested tree structure based on .qlr files. The layer tree is nested according to the location in folder/subfolder of the .qlr files.
A Danish installation manual can be found in the the wiki. Note - this is a guide to installation in QGIS 2.18.
Be aware that currently (May 2019) there is a problem with saving qlr-files in QGIS 3. This is reported as a bug in the QGIS issue tracker: https://issues.qgis.org/issues/19672.