Breaking this down:
1) Testing the fix for bookmark
2) Testing if any other changes in SynEdit are of interest to you
2 can be used for testing 1 too...
1)
- Wait for Lazarus 4.4 (probably a week or so) / The fix will be in there
- Start with Lazarus 4.0 or 4.2 and apply the patch
https://gitlab.com/freepascal.org/lazarus/lazarus/-/commit/cfb8e043815b3e02666b01cf3f63c070a1532799.diff Using the "patch" command line util. If memory serves
cd path/to/lazarus
patch < diff_file
or maybe "patch -p1 < diff_file". If you are in the lazarus main dir, if you are in the Synedit dir it will probably be -p3
- Instead of applying the patch, edit the file by hand.
- use fpcupdeluxe
2) You nee the git "main" branch, aka Lazarus 4.99. Since changes may also be in the LCL.
For that use fpcupdeluxe. It can create an independent install, so your main install will not be altered.
However, I am not an expert on fpcupdeluxe. There is a big thread on the forum, for getting help.
FpcUpDeluxe allows to install any version, including "fixes-4" (which is the preparation for Laz4.4 and then will be prep for 4.6), and "main" aka 4.99 or trunk.
FpcUpDeluxe can install several Lazarus versions in different folders, and those use diff configs, and all. So they all work independently.
Downloading SynEdit independent of the IDE, will be a lot of work, and may even not work at all. Since each version of SynEdit requires the correct LCL, LCLBase, LazUtils, etc. In some cases those may be compatible, but there is no rule when they are and when not.