You can modify DefaultTextMaterialOpaque material, that is by default assigned to text render actor, and change it to be translucent instead of masked (blend mode in material). Then you should multiply input of this opacity by your control value that goes from 0 to 1 (appearing) and 1 to 0 (disappearing). You can use material collection parameter for this purpose (to have a variable inside a material, which then you can change via sequencer).