Post away - this is what the forum is for 😉
Yes you can open up a pop-up form on button press. This would be a regular form, with all options available (inputs, lists, calendars, functions, states, etc.). Often used to create child records or to lookup data from connected records.
If you need to process data from the parent form and use it on the pop-up form: You either need to load data via relation (this works if the data on the parent form was saved beforehand) or you can use frontend-functions to store and retrieve data (see 'value_store') inside the client (e. g. the browser).