The eaist way to for testing is:

1. Download the repo, compile and replace the dll files

2. Copy the whole %repo_dir%\reactivedrop\content\trace_player_ui into %game_dir%\reactivedrop\addons folder and create a dummy addoninfo.txt file like this

"AddonInfo"
{
addontitle "trace_player_ui"
addonauthor ""
addondescription ""
}

Start the game. That should work. Note that you cant see yourself's trace by default. To see your character's trace, open VS, search for std::vector<int> g_nTracePlayer2Color = std::vector<int>, replace the 0 with 1 in both line 122 and line 123. like the following pic. Recompile and replace dlls.

If the UI buttons are not shown up. that's due to the res files are not correctly loaded. The following steps will force load the new res files.
3. Open VS and search "auto currentScheme = rd_legacy_ui.GetString();" in all files. 4 items will show up in search result.
4. Click on each result. Add _1 to all .res file names. like below. there are 8 file names total. Recompile and replace dlls.

5. rename 8 new .res files in %game_dir%\reactivedrop\addons\trace_player_ui\resource\ui to _1.res.