By default REAPER uses system cursors, or these cursors that are embedded within the program. Almost all cursor uses may be overridden with your own cursors, see Theming Cursors.
Find you REAPER resource path by choosing "Options > Show REAPER resource path in explorer/finder..."
Locate the 'Cursors' folder.
Valid .cur cursor files placed within that folder will override the default cursor of the same name. A REAPER restart is required to enable the override.
arrange_itemvol
The item's volume adjustment when the preference 'Ajust media item volume by dragging' is set to 'top edge of media item'. Defaults to 'double headed vertical arrow' system cursor.
itemfx_dd_no
Drag item FX to an unsupported location. Defaults to slashed circle system cursor.
xfade_curve
(Mouse Modifiers > Media item fade/autocrossfade > left drag > Adjust fade curve) Drag-adjust the curvature of a crossfade. Defaults to XFADE_CURVE
midi_note
Select / move a note. Defaults to arrow system cursor.
midi_noteedge
Resize a note. Defaults to left/right arrow system cursor.
midi_paint
(Ctrl+Alt) Left-drag paint notes. Defaults to BRUSH.
midi_vol
Adjust a note's velocity using the note's velocity bar. Defaults to up/down arrow system cursor.
midi_vel
(Alt) Adjust a note's velocity. Defaults to up/down arrow system cursor.
midi_vellane_size
Resize a CC lane. Defaults to up/down arrow system cursor.
midi_arp
(Shft+Alt) Arpeggiate timing of notes. Defaults to ARP.
midi_bg
(Mouse Modifiers > MIDI piano roll > left drag > Default action > No Action) Left dragging in empty space will do nothing. Defaults to arrow system cursor.
midi_chord
(Mouse Modifiers > MIDI note > left drag >stretch notes (arpeggiate) > vertically) Arpeggiate pitch of notes. Defaults to CHORD.