How to add more shortcuts per row?

I prefer you to use use bookmarks than homepage shortcut , if you visit any websites "control+D" bookmarks them , you can then use "control + shift + O" , to see all your your bookmarks ( you can make folders if you prefers ) , then in "keywords" just name of your interest , like to access "gemini" for "ge" .So when you open firefox "control L" to access the search bar , then you type "ge" press enter , now you taken to gemini , i think the default number of shortcut in homepage is 4 you may increase to 8 but beyond that you need to use other addons (tabliss , nighttab, but i dont tried them , try if you wish ) ,but bookmark can hold any number of website you wish , i hope it is helpful to you