Reaper v5.40 is a new version update from the v5.3 versions. The newer version features include Spectrogram Peak and Swing Grid. There is a video link of the new version. A few of the new instructions include the following:
(On the Video in sec.)
00:18 Instructions on audio pre-roll. Navigate back to pre-roll recording.
2:25 To adjust project tempo adjust REX; should not resample.
2:25 To stretch media adjust REX; should not resample.
At the end there are several links, to the Reaper download, for the RedPack extension, and to Reaper blogs at Twitter, Facebook and Patreon.