If somebody is sincerely taking part in a futile or unneeded task with/for somebody, but rather than giving up, not bothering or flat out refusing they go along with it, not to humour them, but to show support and kindness.
With only a <blank> she made to help her friend up after falling over, although she knew between her own strength and her friend's weight meant it would have made no difference; regardless they both knew she was more than capable of getting up by herself, but the <blank> was appreciated.
Applying for the job was only a <blank>, as Alex knew they were underqualified and had no intention of accepting an offer, but they also knew it would reassure their friend to know they hadn't applied alone.
He offered to buy food for the barista at the coffee shop, despite knowing he'd say no. It was a <blank>, but still meant a lot to the barista.
Ze put zir hand out as she got off the bus, ultimately a <blank>, as she didn't need helping and subsequently didn't lean any of her weight on zir. Rather than being offended by zir, the obvious <blank> made her smile.
Nugatory and performative seem too negative for my purposes. The phrase 'kind gesture' doesn't communicate that the one making it thinks it's not going to work or is not needed. Saying "It's the thought that counts" implies to me the gesture might have been sincere, but failure/lack of outcome wasn't a foregone conclusion.
What can I use to get this idea across?