is it possible to group items in ms word and apply formatting change to all of that group only at the same time, so that you dont have to format everything everytime you make a change?

for example. i am writing a long text like a book. it has main titles, subtitles, highlighted text, normal text and formula text.

when or if i want to make a change to one of these groups, i have to change everything in that group one by one. for examplke i want to reduce the font of my text by 1 point now. but my book is already at 90 pages. so i must go through 90 pages of text, skipping titles and subtitels, select main text one by one, and reduce the font. but if that main text was in a group called "main text" for instance, i could have easily done it by changing the group format only. is this possible in ms word?

for someone who is familiar with web coding, i am talking something similar to using CSS, or for example the equivalent of layers in autocad.