When specifying the enable condition, it is not possible to specify liquid signals or logical signals (for example letters)

This is working for me on 1.0.7

Are you sure you have latest version? If so, could you upload your save (possibly a fresh one with your mods enabled) somewhere?

I checked the list of mods - your mod conflicts with "Attach Notes" (https://mods.factorio.com/mod/attach-notes). I think we need to add it to the conflict list (there is no point in looking for a solution)

I fixed signals in 1.0.8, however, Attach Notes still doesn't work with pumps and wagons because of the way entity windows are handled. Basically any entity that has its window replaced by a moded one doesn't work with Attach Notes