I'm still learning on modding bios (mostly just asus so let learn more about dell), so let me put in some of the stuffs I have figure out on your bios:
Here is the full IFR of the setup module: https://a.pomf.cat/tsslli.txt
Below is the part of the menu tab:
0x187C6 Form: Setup, Form ID: 0x2715 {01 86 15 27 06 00}
0x187CC Ref: Main, Variable: 0xFFFF {0F 0F 08 00 02 00 25 00 00 00 FF FF 00 16 27}
0x187DB Ref: Advanced, Variable: 0xFFFF {0F 0F 1D 00 02 00 26 00 00 00 FF FF 00 17 27}
0x187EA Ref: Chipset, Variable: 0xFFFF {0F 0F 1E 00 02 00 27 00 00 00 FF FF 00 1A 27}
0x187F9 Ref: Security, Variable: 0xFFFF {0F 0F 2D 00 02 00 28 00 00 00 FF FF 00 1B 27}
0x18808 Ref: Boot, Variable: 0xFFFF {0F 0F 1F 00 02 00 29 00 00 00 FF FF 00 1C 27}
0x18817 Ref: Save & Exit, Variable: 0xFFFF {0F 0F 40 00 02 00 2A 00 00 00 FF FF 00 1E 27}
0x18826 End Form {29 02}
Your Root Port 3 Hot Plug part:
0x2402C Setting: Hot Plug, Variable: 0x358 {05 91 78 07 79 07 C8 03 01 00 58 03 10 10 00 01 00}
0x2403D Option: Disabled, Value: 0x0 {09 07 36 06 30 00 00}
0x24044 Option: Enabled, Value: 0x1 {09 07 35 06 00 00 01}
0x2404B End of Options {29 02}
I'm still unable to find the variable making the chipset availaible to user (asus bios was just an array of boolean), its appears that to show chipset menu we have to manually edit every "Suppress If" value and that is beyond me (for now). Basically if any one have a better understanding of how the module in hex (not me sr) could hard set the optimal value of the Hot Plug variable then repack it with UEFITool, its should work. I spent way too many time on this instead of my upcoming exam so I cannot dig any further, but if someone know how to change these hex value correctly please guide us.