http://www.adamwathan.com/reaper/AWPerformanceCorrectionToolbar.zip
Just import the MenuSet file and the KeyMap file. It'll replace whatever you have as Floating Toolbar 2 though so be careful.
The text icons make it hard to see what the buttons do :/ But the first one is the "split at transient to right of mouse cursor" tool, you right click it to arm it and then click around.
Second button just opens Dynamic split (make sure not to use any of the extra features in there if you are using my smoothing tool ie. NO LEADING PAD and NO AUTO ADJUST SNAP OFFSET, my smoothing action does that for you and does a better job, things won't work if you try and do it twice)
Third button opens the "Quantize Item Positions" dialog, I don't use it that often, but if you do DO NOT USE ANY OF THE EXTRA FEATURES. No "extend starts...", "shorten earlier..." or "stretch to fit" or whatever. The only checkbox that should be checked is "move grouped items with selected items".
Fourth button is a "quick quantize", just press it and it'll quantize selected items to the nearest grid line based on your grid setting. This is the one I use a lot, waste of time opening the dialog when you could just use this, especially when you aren't allowed to use any of the other quantize features
Fifth button opens the advanced smoothing dialog. This is the bread and butter of the whole thing, watch the videos to learn how to use the parameters. I've found that Max Gap is better off around 15ms and Max Stretch is better around 0.5. Stretching to fill a big gap always sounds better than backfilling, even if the stretching still doesn't sound perfect, so better to let it stretch it alot if it has to instead of doubling the transient. Preserve Transient is good where it is as is the Trans Fade Length.
6th button I believe is Fill Gaps with no Crossfade, just quickly fills the gaps, no stretching, no dialog.
7th is the same but it adds a crossfade of the "Default fade length" set in the preferences.