No, I’m afraid a moisturizer won’t help with bladder function. Moisturizers really only improve the tissue condition in the vagina where they’re applied.
The vagina and the base of the bladder and urethra do have some tissue characteristics in common–they have the same embryonic origin. They both, for example, have estrogen receptors. That means that localized estrogen in the vagina can influence bladder function like frequency and urgency. Estrogen for localized application comes in several forms, but moisturizers don’t contain estrogen.
If you are bothered by urinary urgency or frequency, I’d encourage you to see your medical practitioner; there can be multiple causes and there are solutions for each!