This might be helpful:
In the Text Layer options you have the Source text, this can create Hold keyframes (square keyframes) which do not have interpolation, simply change everything you have in the Character panel but it does not touch the transform properties as you see in screencaptures, transform properties are for the layer, not for the text of the Text Layer.
Turn on Source Text keyframes and adjust your text however you want it initially, then move forward a few frames with the playhead and adjust any settings in the Character panel (remember, don't touch the transform properties). This way you will see how the text changes in each Hold keyframe.
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