Hi
Note that if you use the Position effect you don't set up your text to scroll. You just move the text image using position keyframes as Borate shows.
As an alternative to using Position....
Before you add anything to the video tracks.....
Create your left to right scrolling text. It will save to the image bin.
Place this image onto Video Track1 and adjust its scrolling speed by dragging the ends of the clip in/out.
Save Video track 1 as a Sequence.
Your scrolling text will now be in the sequence bin and Track 1 will now be empty.
Drop the sequence (your scrolling text) back onto Video track 1
Play it to where it is central by sliding the cursor (or playing the clip) and take a snapshot. This will also arrive in the image bin. Don't move the cursor.
Using the drop-down menu options, place the snapshot on the sequence at the cursor position. It will insert as a new clip.
Drag the ends of the snapshot clip in or out until still phase is suitable.
Your text will scroll across and stop and then scroll off.
You can group the three clips together before moving them as a single unit up to the overlay track or you can create another sequence and place this on the overlay track.
Note. You must use a sequence for this procedure or the scroll will restart from the left after the inserted still image.
Nat