@csaggo.com
I personally add the three classes in my frontend css on every processwire project. The rules are also for the old editor.
.align_left {
text-align: left;
}
.align_center {
text-align: center;
}
.align_right {
text-align: right;
}
When i know, there will be a conflict with other align rules, i set also !important.
For uikit, you can add this rule in the site.scss, like here explained: https://getuikit.com/docs/sass#how-to-build the "// 1. Your custom variables and variable overwrites." section in the example code.