I understand that you can reuse existing Pro controls on a custom tab using their refID, and you can obtain that refID from this document: ArcGIS Pro DAML ID Reference · Esri/arcgis-pro-sdk Wiki · GitHub
But when you reference a button inside a tab or group you can't access some of its properties, like Caption. For instance, if I want to use the esri_mapping_clearSelectionButton and esri_editing_ShowAttributes on my own tab, how do I get the captions?

If I add those tools to a group on my own tab I can't get the captions to appear:

You can't add the caption when you reference the tools here:
<group id="MyFavoriteGroupOfTools" caption="My Favorite Tools" appearsOnAddInTab="false">
<button refID="esri_editing_ShowAttributes" size="small"/>
<button refID="esri_mapping_clearSelectionButton" size="small"/>
</group>
Other questions about reusing tools:
Why does the Show Attributes tool look fine when both small and large, but the Clear Selection button doesn't seem to have a large icon?
Can you use an existing control but provide your own icon for it?