In this thread i'll post some short GIF clips where elementary actions are showcased. 
I'll post one each post so they may be commented in subthreads. 

These GIF:s are the byproduct of semi-regular documentation sessions i hold on my Patreon blog and its dedicated discord. 

  Quickly selecting colour and subpalette:

Box selection.

Select tile by reference. 

Swap tile places.

Using colour protect masks, example 1:



Using colour protect masks, example 2:



Observe that the mask buttons can be controlled in group if you click on them with modifier keys. 
Hold the mouse hovering over one of the 4 buttons to read the options available in the status bar.

• Using Brush
• Using brush with quantize mode
• Using brush with brush mask
  
  
  

Pen / brush can be toggled with [B] in CHR Editor, or with [Shift+B] anywhere. 

Quantize mode can be toggled with [N} in CHR Editor, or with [Shidt+N] anywhere.

Brush Mask Editor can be opened with [M] in CHR Editor, or by right-clicking [Brush] button, or with [Shift+F4] anywhere. 

Removing unused tiles, sorting the remainder. 
Note that the metasprite automatically re-indexes its tile references. This is new in NEXXT.

New in nexxt 0.18.3 - give unused (or duplicate) tiles an ID pattern.

a) menu > patterns > Find unused (or Ctrl + U)
b) menu > patterns > generate > Fill tiles with numbers
c) Deselect (Ctrl + Shift + A)