What I tend to do is a search of the data sheet for the peripheral pin I want, and Table 15 shows me which GPIO it shares, and what pin (if any) it is bonded to.
If I look in the data sheet for STM32L4R5xx, STM32L4R7xx and STM32L4R9xx DS12023 Rev 4 in Table 15
on page 97/310, I can see which pin PD11 is connected to (for LQFP100 this is not connected) and that one of its alternate functions is LCD_R6. So you can't use LCD_R6 if you have the LQFP100 package.
Similarly, on page 98/310, I see that LCD_R7 is PD12, again unavailable in LQFP100.
And on page 115/310, LCD_HSYNC is PE0 and LCD_VSYNC is PE1. But neither of them is bonded out for the LQFP100 package.
That's just one of the compromises of a package with fewer pins.
If you've chosen LQFP100 due to board size limitations, you might consider a BGA package. But they tend to need more complicated pcbs.
Hope this helps,
Danish
