I've just spent nearly two hours tracking down  a nasty crash caused by increasing a buffer declared within a function (ie on the stack) from 1024 bytes to 4096 bytes. Of course I did lots of code after doing this and before doing a compile so I had no clue that this was the root cause.

Lesson is... embedded programming is substantially different than Windows/Linux development so small changes, like in this instance only 3KB, can cause a problem. I have ended up using far more globals than I would normally in Windows/Linux dev. Also the Arduino IDE is designed for absolute beginners, which is great as it gives the lowest level of friction for progressing quickly with your embedded projects, however it does pretty much force you to use one code file (not even a .c file, it has to be suffixed .ino) and it is a bit strange in its behaviour when compiling. eg you don't need function prototypes forward declared of their first usage (where the function code is below in the text file than the call). This also results in rather misleading error messages when compiling too. However, I can't complain - it's been great to not have the bloat of visual studio with all the admin stuff that is associated with.

However, when I get back from my dive trip to Gozo it will be high time to bid adieu to the Arduino IDE and setup either PlatformIO or Visual Studio Code.

Here's some really detailed info on how to reduce memory usage, which also mentions minimise the use of the stack. It's for the Espressif dev environment but it's fair to assume the guidance crosses over to the Arduino IDE / build environment:

Espressif API Guide - Minimise RAM Usage