What does "tickable" mean?

That can be ticked; capable of being marked with a tick or check mark.

Tickable

/ˈtɪkəbəl/ adj

adj ·Rare ·Advanced level

Adjective

1
That can be ticked; capable of being marked with a tick or check mark. not-comparable
"tickable boxes in a questionnaire"
2
Of a bird, located so that it may be travelled to and viewed. not-comparable
3
Of an observation, good enough to ensure correct identification and therefore allow the bird to be added to a list of observed birds. not-comparable
"On landing the dark forms of the jungle fowl could be seen scattering across the airfield, but we were moving too fast for me to get a tickable view."
4
Of a program instruction: counted for the purpose of generating periodic signals every few instructions. not-comparable
"A tick is an event that occurs for every N low-level tickable statements executed by the parser within the declare block."

"tickable boxes in a questionnaire"

From tick + -able.