General Tips

Turn off things like synths when you are done using them. Export an audio of the synth soloed to an audiofile and "save-as" the song to another number "song23, song24" etc... turning off synths when you are done with them saves cpu and memory. make audio of your synth parts, then you can edit them and do things...with the scissors tool... Edited Audio is the sound of today- Leaving your synth parts as midi makes it difficult to edit. The reasons for editing can range from:
1) adjusting the timing- to compensate for the way a sound opens up in time
2) keeping only the best little bits to make a composite/synthetic "riff" that was never actually played that way in MIDI
3) processing each bit of audio for your production.
4) the biggest reason of all: you can actually SEE your audio result of your synth sound and whatever anomalies may exist. Without audio you are operating somewhat in the dark...

Cubase/Nuendo Tips:

Make the key commands for things like "process--reverse, process--bounce,file--export mixdown, file--import audio" etc... file--keycommands

Look at the preferences. Many things can be set here.
Things like AutoTrackZoom, AlwaysOnTop for Plugins, AssumeNewVersions for audio processes, etc...file--preferences

F11 is your VST rack. Turn off synths when you are done using them. Export your soloed synth as Audio. Save the song, Save-As a different number, and then turn off the synth. This will save CPU and memory.

Try pressing "alt"and using the scissor tool on an audio clip... it
slices the whole clip.

g and h are zoom in/out.

Control D duplicates a part right after itself.

Holding alt while click-dragging makes a copy.

The "vst-instruments" track and the "synth whatever" tracks inside it are just FOLDER tracks... not really even tracks... just folder objects that hold things... you can move things around inside and put your midi tracks in there too...