TL;DR maybe yes... but it depends, should CYLOR just to be safe
Rav Yosef Yeshaya Braun in a chabadinfo.com article titled "Can I Buy my Seat With Maaser Money?" says it depends:
There is a discussion among contemporary poskim whether maaser (one tenth of one’s earnings that is earmarked for tzedakah) may be used to purchase a seat [for the High Holy Days].
According to many poskim, maaser money may be used not only for tzedekah but also towards fulfilling certain non-obligatory mitzvos.
However, buying a seat in shul does not fall under that category [of being able to be used for non-obligatory mitzvot]. Davening in shul is a mitzvah, but having a seat simply facilitates the mitzvah by adding to the person’s comfort; albeit they will be davening with more kavanah, which is considered a mitzvah, it doesn’t justify spending maaser money for it.
Whereas money goes to the shul, they are actually buying a product for themselves – a seat – which has market value.
R' Braun writes how he believes there are instances when maaser money can be used to buy Yomim Noraim seats.
However, if one owns a seat permanently, or if there are many empty seats in their shul and they are buying a seat in order to support the shul, they can certainly pay for it with maaser money.
In the same vein, if the shul sells more expensive seats and less expensive ones, and one buys the more expensive seat when they could have managed just as well with a less expensive one, then they may use their maaser money to pay for the difference between the cheaper seat and the one they are buying.
Rav Akiva Dershowitz of tvunah.org takes a more lenient approach:
Being that the money is going to a shul, which is certainly a valid recipient of maaser and tzedaka, buying a seat for Rosh Hashana and Yom Kippur would also be permitted. The Taz [YD: 249] permits using maaser money for a wide range of mitzvos, but here where the money is going to a shul, this would certainly qualify for maaser. The only issue would be that maaser can’t be spent on something one has to spend money for anyway, which would be paying one’s debt with maser, in a sense. However here, since strictly speaking one is not required to purchase a seat in the shul, as he could daven somewhere else or in the shul and stand for davening. Hence, purchasing a seat is not comparable to paying one’s debt and may be done with maaser ksafim.