Shotcut 20.11.28
Windows 10 Home 64bit i5
When creating a Text: Rich filter, the content of the last created filter displays throughout the entire timeline, regardless of the keyframe IN and OUT settings. The exported video displays as intended, but this is a major distraction when editing.
The workaround was obvious once the problem was diagnosed: Create a blank Text: Rich filter as the last item on the timeline.
Is this still true if you select a different filter in the filters panel?
Yes, based on a sample of one - Crop: Circle.
It may be that any other filter clears its mind. I only checked one.
The Text: Simple filter did not exhibit this problem at all.
I do not reproduce, and you have not included steps to explain it well.
You are probably seeing the rich text editor, which is separate from the actual video filter. The editor shows for the entire duration of the item to which it is applied regardless of filter in and out points in Keyframes. For now, you need to understand this behavioral quirk and click the X button in Filters to deselect the filter.