First: let's set 2 thing apart.
(1) entry in the General Journal page allows for the use of a foreign currency, as Judy shows in her reply. But that is NOT your question.
(2) Table 17 (GL Entry) does NOT have the foreign currency notion: all entries are "translated' into your LCY (Local Currency)
Sop trying to find the original currency and FX-amount in T17, will not be possible.
However, the data will always be there in the corresponding document: look in the subledgers (Bank Account Ledger Entries, Customer Ledger Entries, Vendor Ledger Entries,L...) : For it is a customer that pays you in his currency, on a particular date... using a certain rate.
On topic:
If you try to test a Finance Charge memo, try not posting it against a GL Account in a Gen Journal... it simply makes no sense, because it does not say who the Memo is for. It is simply hanging there in thin air.
Create an Issued Reminder including posting Finance Charges for an actual Customer instead. This registration will generate Customer Ledger Entries (CLE) for you
You will find the Currency Code, Currency Factor and LCY amounts in the CLE.
Apply the entries by settling the Finance Charge memo... if there is a FX difference, you will need GL accounts for the FX Loss/ Gain set on you Currency.