What's the noun for supportiveness? Here's the word you're looking for.
support
Something which supports. Often used attributively, as a complement or supplement to.
Financial or other help.
Answers to questions and resolution of problems regarding something sold.
(mathematics) in relation to a function, the set of points where the function is not zero, or the closure of that set.
(fuzzy set theory) A set whose elements are at least partially included in a given fuzzy set (i.e., whose grade of membership in that fuzzy set is strictly greater than zero).
“Let none other be heard among us than those of a good citizen, an open and resolute friend, and a virtuous supporter of the rights of mankind and of the free.”
“Eventually, the man became a supporter of animal rights.”
“Margaret Nightingale has been a constant and loyal supporter of my work for years.”
supportability
The characteristics of a non-consumable product that allow it to continue being useful at low cost.
“It will entail improvements to self-defence and war-fighting capabilities and enhancement to the ship's reliability, maintainability, availability and supportability.”
“The list of evaluation criteria spans quality, performance, application compatibility, and supportability.”