The first PR is done, there are just some failures of the CIs related to issues with updates in other packages https://github.com/mne-tools/mne-python/pull/10777! This PR abstracts the slice browser from the ieeg locate GUI so that it can be used in the time-frequency viewer. Instead of calling Qt widgets directly, another step (not in the timeline) that would be great would be to abstract the widgets so that they will work on either the Qt backend or a notebook backend. The original first PR plan has been discussed https://github.com/mne-tools/mne-python/issues/10721 but, after talking to Britta, the thought was to delay this a beat to see more what the GUI would look like and plan the input to match (as well as waiting for any progress of Dan's refactoring of TFR classes to harmonize with that).