The visualisation in the attribute table is different for fields with the same data type (some are greyed out and the values have different positions)
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You can right click on the layer to open its properties and go to the Attribute Form tab.
editable will enable/disable (and grey out) the field.
range will let you "scroll" through numerical values and will right-align the number.
Text edit will let your type a value and left-align it.