Visible Custom Items: https://app.roll20.net/forum/post/3346285/script-turn-tracker-automatically-add-custom-item-w-slash-round-calculations/?pageforid=3346527#post-3346527
Invisible Custom Items: https://app.roll20.net/forum/post/6606108/hidden-custom-turn-order-items/?pageforid=6606389#post-6606389
Here's the macro I use to add spell effects to the Turn Tracker:
!?{Visible or Hidden?|Visible,act|Hidden,aict} ?{Countdown Number|-1} ?{Number of Turns|10} --?{Caster|@{selected|token_name} Spell}: "?{Effect Name|BlessSleepEtc}" ?{Concentration?||Yes,«Concentration» |No, |}
Those scripts are set up to add the custom items to the top of the turn tracker. I changed a line of code in each to add the bottom of the tracker instead. Replace the lines with to.unshift({ with to.push({ if you want that as well.
to.unshift({
to.push({
There's probably a way to add the custom items in specific place in the turn order, but that's out of the scope of how the script is currently written. As is you can still add them and then you'd be able to manually move them to the correct place.