Sometimes Power Automate is trying to be helpful by limiting options based on field type. For example if you want to insert data into a datetime field, PA won't show dynamic content that are string/text type.
This isn't always helpful, and PA isn't always accurate.
You can manually put the 'dynamic content' into an expression and it should work.
The easiest way to manually put in dynamic content is to add a Compose step. The dynamic content should be available to put into that Compose. (If it is not available for the Compose then you have a different problem.)
Highlight and copy the dynamic content and past it into like a text/notebook.
Highlight Dynamic Content - Paste into Text
Then go to the Excel field you want to add the dynamic content and paste in the text to the expression.
Make sure you remove the '@{}' from the copy and pasted dynamic content.
This may seem like a hassle, but I have to do this all of the time when using expressions.
