So you got a new computer and/or display – and it’s whiz-bang 4/5k resolution.
This is amazing! it means you can now see all 1,000,000 of your Excel rows in a single glance 
What you may ALSO notice if you’re using SQL Developer with Java 8, is a tiny user interface – the fonts and images will be the same ‘size’ they normally are, but if you have Application Scaling enabled for your OS, SQL Developer won’t get ‘bigger.’
This is of course a subjective position, but let’s assume you are in the ‘why is everything so small!’ camp, you may see something like this –
With Java 11/12, and setting the Scale and layout to 150% –
Ok, so how do I tell SQL Developer to use Java 11?
Step 1: use at LEAST version 19.2 of Oracle SQL Developer.
Step 2: Install Oracle JDK 11/12 (OpenJDK is not supported, but will probably work)
Step 3 Windows: Find your AppData – Roaming – sqldeveloper – X.Y.Z – product.conf file
For example on MY machine, that’s here
C:\Users\jdsmith\AppData\Roaming\sqldeveloper\19.2.0
Step 3 OS X: Find your $HOME/.sqldeveloper/product.conf file
In that file – make THIS change –
Then just open SQL Developer, go to your OS settings where the Display preferences are, and as you adjust, you should see SQL Developer’s UI change as well.
I tried this on latest OS X with a 4k Dispay and Windows 10 with a standard ‘regular’ monitor.
There are various other ways to address this issue, and you’ll see them discussed on StackOverflow and in the blog-osphere…including my post where I show you how to actually increase the FONT size of the UI, but I think this will be ultimately the cleaner solution going forward.
In the meantime, hopefully I can stay at 20/20 a bit longer.
