flattening a sequence in Adobe Premiere (collapsing included sequences)
(1.) Open the master sequence containing the nested sequences.

(2.) MAKE SURE that the "Insert or overwrite sequences as nests or individual clips" selector (the leftmost icon under the timecode display in the sequence panel) is NOT highlighted. This will force a nested sequence in the Source Monitor to be edited into the sequence as the individual clips contained in the nested sequence.


(3.) Park the playhead in the middle of one of the nested items in the main sequence

(4.) Choose "Marker / MARK CLIP" (I have this programmed to "X" on the keyboard.") You need to make sure your track selection toggles are correctly set to target the track containing the nested item.

(5.) Choose "Sequence / MATCH FRAME" (I have this programmed to "F" on the keyboard.) This opens the nested sequence into the Source Monitor.

(6.) Choose "Clip / OVERWRITE" (I have this programmed to "B" on the keyboard, like an Avid.) This should have replaced the nested sequence CLIP ITEM with the clips contained in the nested sequence. This overwrites (from IN to OUT as selected in step 4) with the contents of the nested sequence.

(7.) move the playhead to the next clip and press X, F, B

(8.) repeat step 7 until you're done.

[This is tested on Premiere CC 2015.2]