I thought it is the same way?
In any edit mode of text (for example in XDA app, need to be in quote mode)
just tab on text and hold, a set of place markers will appear. Just adjust the start and end, and hit copy icon on top.
for paste just hit a blank spot and a paste icon will appear.
Can you please provide a link to rotto's modem switcher? Do i just flash in odin via" phone" category? Thanks again!