Just after upgrading to Trixie noticed that ..
Multiple invocation/configuration with raspi-config -> Display Options -> D2 Screenblanking -> enable screenblanking "Yes" -> OK
results in getting multiple swayidle -w timeout 600 'wlopm --off \*' resume 'wlopm --on \*' & lines in ~/.config/labwc/autostart. and starting more and more swayidle processes.
raspi-config seems not to check whether a line with the same parameters/options is already existing.