Mods can't access the savefile directly, so the mod tracks itself witch items are taken. This means that the first time you install it, everything will be marked as new.
If you want to import data from your savefile, you can either use the extractor I wrote (adapting EID's one for Linux), or install Repentogon.
The extractor is available here : https://forge.chapril.org/ayte/DeadGodHelper/src/branch/main/SaveExtractor
This mod is still relevant in itself if you do not want to use external tools, or you want to track modded items ^^