Commonly used forms like Sales orders or Projects in Dynamics AX have multiple grids. Normally, one grid is in the upper section and another one is in the bottom section of the form. Sometimes grids are placed next to each other.
The size of the data in each grid may vary, and that's why most of the forms with multiple grids have splitters in the middle so users can resize both grids at once by dragging the splitter with the help of a mouse. It is a good practice to add splitters to newly created forms.
Although Microsoft developers did a good job by adding splitters to most of the multi-grid forms, there is still at least one that has not got it. It is the Account reconciliation form in the Bank module, which is one of the most commonly used forms. It can be opened from Bank | Bank Account Details, Functions | Account reconciliation button, and then the Transactions button. In the following screenshot, you can see that the size of the bottom grid cannot be changed:
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