Using Unity 2023.2.2f1, Inventory System 1.2.18 (for some reason .19 is not available for download via Package Manager)
Able to Duplicate and setup UI without issue however. Can also create a UI e.g. an Inventory Grid. However, when trying to make any additional edits of UI get 29 instances of this error:
NullReferenceException: Object reference not set to an instance of an object
UnityEngine.UIElements.TextElement.get_showPlaceholderText () (at <88a51cb7a4604f61859dafad483fe0d4>:0)
UnityEngine.UIElements.TextElement.get_renderedText () (at <88a51cb7a4604f61859dafad483fe0d4>:0)
UnityEngine.UIElements.UITKTextHandle.ConvertUssToTextGenerationSettings () (at <88a51cb7a4604f61859dafad483fe0d4>:0)
UnityEngine.UIElements.UITKTextJobSystem+PrepareTextJobData.Execute (System.Int32 index) (at <88a51cb7a4604f61859dafad483fe0d4>:0)
Unity.Jobs.IJobParallelForExtensions+ParallelForJobStruct`1[T].Execute (T& jobData, System.IntPtr additionalPtr, System.IntPtr bufferRangePatchData, Unity.Jobs.LowLevel.Unsafe.JobRanges& ranges, System.Int32 jobIndex) (at <454b8adca03e44db8a0e3ace7093e9b8>:0)
Also the UI Designer goes completely blank.

If I delete the object (e.g. the said inventory Grid) then the UI Designer gets back to stable state and I can recreate the UI... however same problem will re occur.
This happens with the Demo Database as well with a custom one.
Thanks for looking at this.. - S
Able to Duplicate and setup UI without issue however. Can also create a UI e.g. an Inventory Grid. However, when trying to make any additional edits of UI get 29 instances of this error:
NullReferenceException: Object reference not set to an instance of an object
UnityEngine.UIElements.TextElement.get_showPlaceholderText () (at <88a51cb7a4604f61859dafad483fe0d4>:0)
UnityEngine.UIElements.TextElement.get_renderedText () (at <88a51cb7a4604f61859dafad483fe0d4>:0)
UnityEngine.UIElements.UITKTextHandle.ConvertUssToTextGenerationSettings () (at <88a51cb7a4604f61859dafad483fe0d4>:0)
UnityEngine.UIElements.UITKTextJobSystem+PrepareTextJobData.Execute (System.Int32 index) (at <88a51cb7a4604f61859dafad483fe0d4>:0)
Unity.Jobs.IJobParallelForExtensions+ParallelForJobStruct`1[T].Execute (T& jobData, System.IntPtr additionalPtr, System.IntPtr bufferRangePatchData, Unity.Jobs.LowLevel.Unsafe.JobRanges& ranges, System.Int32 jobIndex) (at <454b8adca03e44db8a0e3ace7093e9b8>:0)
Also the UI Designer goes completely blank.

If I delete the object (e.g. the said inventory Grid) then the UI Designer gets back to stable state and I can recreate the UI... however same problem will re occur.
This happens with the Demo Database as well with a custom one.
Thanks for looking at this.. - S