Short answer
Run defaults write com.apple.dock persistent-apps -array-add '{"tile-type"="spacer-tile";}'; killall Dock in Terminal. A blank space appears at the end of your apps. Drag it where you want it. To remove it, drag it out of the Dock.
macOS has no button for this, but the Dock has supported blank spacer tiles for years. Spacers let you group apps, for example browsers together, then a gap, then your code tools. It makes a long Dock much faster to scan.
Add a normal spacer
Open Terminal and run:
defaults write com.apple.dock persistent-apps -array-add '{"tile-type"="spacer-tile";}'; killall DockRun it once for each spacer you want. Each one appears at the end of the apps section, and you can drag it anywhere.
Add a smaller spacer
A half width gap looks a little neater:
defaults write com.apple.dock persistent-apps -array-add '{"tile-type"="small-spacer-tile";}'; killall DockAdd a spacer on the right side, near the Trash
The right side of the Dock holds folders and stacks. To put a gap there, use persistent-others instead:
defaults write com.apple.dock persistent-others -array-add '{"tile-type"="spacer-tile";}'; killall DockRemove a spacer
Drag the spacer up out of the Dock until you see Remove, then let go. Or right click it and choose Remove from Dock.
Grouping without the Terminal
DockAlly does this for you. In each Dock profile you put apps into groups, and it writes the gaps into your real Dock when you switch. Your Coding Dock and your Designing Dock can be grouped differently.