(A) 3D straight arrows (cylinder + cone) can be created in the BILD text-file format and read it in.

<http://unicode.org/charts/#symbols>

(B) 2D labels are text labels that can be dragged around in the plane of the graphics window.  Although Chimera also has 2D straight arrows that can be interactively repositioned at either end by dragging, ChimeraX does not have these (yet).  ChimeraX 2D labels can only be text and symbols.  However, symbol characters include both straight and curly arrows, and you can make them all different sizes.  

You just can’t adjust the proportions of the symbol, and you cannot rotate it at all even in the 2D plane (cannot turn it sideways or diagonal), and they are only 2D (will not actually wrap around your bond or objects in 3D space).

ChimeraX also does not yet have the graphical interface to 2D labels that Chimera has, so you have to define them in the 2dlabels command using unicode character codes or character names:

<http://rbvi.ucsf.edu/chimerax/docs/user/commands/2dlabels.html>

It can be a pain to find the unicode for the exact arrow you want, however, even if you don’t mind the other limitations above.

<http://unicode.org/charts/#symbols>

I attach an image with a 2D label made with this command:

2dl create arrow1 text '\u21BB' size 80 color yellow

I didn’t make the icons you showed, but I’m pretty sure that the arrow parts of the icon images were not drawn in ChimeraX.

I hope this helps,

Elaine