+1 for this feature.
For now, a possible workaround is to replace the text using css, for example this work for me:
/* Remove the span text in the 2nd button */
._retool-myTable .-pagination > .-left > button:nth-child(2) > span {
display: none;
}
/* Add another text in the 2nd button */
._retool-myTable .-pagination > .-left > button:nth-child(2):after {
content: "Checkout Selected";
}
myTable
being the name of the table component.