I'm unfamiliar with Macs or any apple computer, so I apologize if this doesn't work.
1. If you go into your Besiege folder/Besiege_Data/SavedMachines, you will find your machines, these will be saved in a .bsg format.
- You can open these files with (on windows) Notepad, hopefully Mac has an equivalent.
- It will look a bit messy, but to my understanding each row (underneath the heading) will have #|#|#|#|#....etc. (# being a number), these will be in order of when you placed the block.
2. In Besiege, change the slider of the item you want to change to something no other item has on your machine
- For example I use 0.27, but it can be anything you want within the parameters.
3. Save the machine
4. Open its .bsg with notepad.
5. Press CTRL+F then type in the number you chose, it will then find it.
- This value will be under the subtitle: PARAMETER TUNER : SLIDER VALUE
6. Change this value to anything you want, but not negative (except flying spirals can be negative).
7. Save the .bsg with CTRL+S
8. Load the machine in Besiege
- you do not need to restart the game.
I hope this wall of text helped, again I'm sorry but I do not own a Mac so I cannot tell you where your besiege files are if they are not where I said, or what program to use if you don't have notepad.
Or, if you know how to install mods, then try installing the No Bounds Mod by ITR, to make that process a lot shorter.
I haven't used it myself because for some weird reason I dislike using mods, even though I essentially do what this mod does the long way... I'm weird don't question it xD
in finder, click on Go (at the top) and then click on Go to folder. Then insert this: /Users/<insert your username here>/Library/Application Support/Steam/steamapps/common/Besiege . Right click on besiege and click on show package contents. Inside the Contents folder, you should find a folder called SavedMachines. Hope this Helps