How do you align left / right a div without using float?

Another way to do something similar is with flexbox on a wrapper element, i.e.,

 .row {
        display: flex;
        justify-content: space-between;
    }

  <div class="row">
        <div>Left</div>
        <div>Right</div>
    </div>

   

In you case here, if you want to right-align that green button, just change the one div to have everything right-aligned:

<div class="action_buttons_header" style="text-align: right;">

The div is already taking up the full width of that section, so just shift the green button the right by right-aligning the text.

you could use things like display: inline-block but I think you would need to set up another div to move it over, if there is nothing going to the left of the button you could use margins to move it into place.

Alternatively but not a good solution, you could position tags; put the encompassing div as position: relative and then the div of the button as position: absolute; right: 0, but like I said this is probably not the best solution

HTML

<div class="parent">
  <div>Left Div</div>
  <div class="right">Right Div</div>
</div>

CSS

.parent {
  position: relative;
}
.right {
    position: absolute;
    right: 0;
}