Hello Juliane,
2D CAD is probably the best tool for your purpose. 3D CAD like FreeCAD are a lot more complicated and you will end by printing 2D drawings for the workshop...
Forum is a place to start for troubleshooting but since you understand English I would recommend the following:
- Wiki : tutorial page (there is an old one in French)
https://dokuwiki.librecad.org/doku.php/usage:tutorials- Video tutorials on Youtube show some basics of 2D drafting and drafting with LibreCAD, some are in French.
- Unfortunately, there is no French translation for the User Manual now:
https://librecad.readthedocs.io/en/latest/index.html. It is a lot but I recommend to read it once.
It is a lot to read but it will make the learning easier and you will save much time afterwards.
Regarding customizable parts, you could edit a dimension value showing "220" mm and add a comment showing it needs to be adapted such as "220 -> a adapter". This will allow to identify quickly the dimensions to be adapted.
Multipage printing can be useful as it enable to print scale 1 drawings on several A4 pages, in case you need to glue drawing on the wood plate before cutting.
Also,
always draw scale 1. The printing is reduced to whatever scale is suitable 1:10, 1:5, 1:20.
When tou have an issue, you can post the drawing on the forum and request for help. In English you will have much more chance to get a feed-back.
Bon courage !
Fabrice
French hobbyist interested in 2D design.