With CCS 5.4.0.00091 and Grace 2.10.02.85:
1) I was able to use Grace to enable the interrupts for UCB0 RXIE / TXIE. The interrupts are enabled in the Grace generated System_graceInit function in System_init.c and the Grace generated InterruptVectors_init.c contains a stub interrupt handler.
2) On the Grace UCB0_B0 Power User Mode screen after selecting 4-pin SPI the only option for UCxSTE is "UCB0STE output off", so this does look like a bug.
As a work-around to configure P1.4 as UCB0STR try going to the GPIO - Port 1 / Port 2 - Register Control page and set bit 4 in the port 1 SEL.x and SEL2.x registers.