more examples of dhamma-vicaya-sambojjhanga in sutta passages, in slightly disguised form

So what you want to notice is that consistently, throughout the EBT, Dhamma is referring to 'the Buddha's teaching' that leads to viraga...Nirvana.
The "Dhamma" in Dhamma-vicaya-sambojjhanga, is not referring to mental-objects, mental-qualities, at least not as the primary meaning.

AN 7.3 Powers in Brief (⤴)

...
Saddhābalaṃ vīriyañca,	“The powers are faith and energy,
hirī ottappiyaṃ balaṃ;	conscience and prudence,
Satibalaṃ samādhi ca,	rememberfulness and undistractible-lucidity,
paññā ve sattamaṃ balaṃ;	and wisdom as the seventh power.
Etehi balavā bhikkhu,	Empowered by these,
sukhaṃ jīvati paṇḍito.	an astute monk lives happily.
Yoniso vicine dhammaṃ,	They should investigate the Dhamma-[teaching] rationally,
paññā-yatthaṃ vipassati;	discerning the meaning with wisdom.
Pajjotasseva nibbānaṃ,	The liberation of their heart
vimokkho hoti cetaso”ti.	is like a lamp that does nirvana.”

(also notice vipassana, a close relative of 4sp Dhamma-anupassana)

AN 7.4 has the same verse as AN 7.3

SN 1.48 Jeta’s Grove (⤴)

48. Jetavanasutta	48. Jeta’s Grove
“Idañhi taṃ jetavanaṃ,	“This is indeed that Jeta’s Grove,
isisaṃghanisevitaṃ;	frequented by the Saṅgha of hermits,
Āvutthaṃ dhammarājena,	where the King of Dhamma stayed:
pītisañjananaṃ mama.	it brings me joy!
Kammaṃ vijjā ca dhammo ca,	Deeds, knowledge, and Dhamma-principle;
sīlaṃ jīvitamuttamaṃ;	ethical conduct, an excellent livelihood;
Etena maccā sujjhanti,	by these are mortals purified,
na gottena dhanena vā.	not by clan or wealth.
Tasmā hi paṇḍito poso,	That’s why an astute person,
sampassaṃ atthamattano;	seeing what’s good for themselves,
Yoniso vicine dhammaṃ,	would examine the teaching rationally,
evaṃ tattha visujjhati.	and thus be purified in it.
Sāriputtova paññāya,	Sāriputta has true wisdom,
sīlena upasamena ca;	ethics, and also peace.
Yopi pāraṅgato bhikkhu,	Any monk who has gone beyond
etāvaparamo siyā”ti.	can at best equal him.”
Notice how Dhamma is used in all those cases.  It's Buddha-teaching, not "mental qualities".

SN 2.20 With Anāthapiṇḍika (⤴)

20. Anāthapiṇḍikasutta	20. With Anāthapiṇḍika
Ekamantaṃ ṭhito kho anāthapiṇḍiko devaputto bhagavato santike imā gāthāyo abhāsi:	Standing to one side, the god Anāthapiṇḍika recited these verses in the Buddha’s presence:
“Idañhi taṃ jetavanaṃ,	“This is indeed that Jeta’s Grove,
isisaṅghanisevitaṃ;	frequented by the Saṅgha of hermits,
Āvutthaṃ dhammarājena,	where the King of Dhamma stayed:
pītisañjananaṃ mama.	it brings me joy!
Kammaṃ vijjā ca dhammo ca,	Deeds, knowledge, and Dhamma- principle;
sīlaṃ jīvitamuttamaṃ;	ethical conduct, an excellent livelihood;
Etena maccā sujjhanti,	by these are mortals purified,
na gottena dhanena vā.	not by clan or wealth.
Tasmā hi paṇḍito poso,	That’s why an astute person,
sampassaṃ atthamattano;	seeing what’s good for themselves,
Yoniso vicine dhammaṃ,	would examine the teaching rationally,
evaṃ tattha visujjhati.	and thus be purified in it.
Sāriputtova paññāya,	Sāriputta has true wisdom,
sīlena upasamena ca;	ethics, and also peace.
Yopi pāraṅgato bhikkhu,	Any monk who has gone beyond
etāvaparamo siyā”ti.	can at best equal him.”
Idamavoca anāthapiṇḍiko devaputto.	This is what the god Anāthapiṇḍika said.
Idaṃ vatvā bhagavantaṃ abhivādetvā padakkhiṇaṃ katvā tatthevantaradhāyi.	Then he bowed and respectfully circled the Buddha, keeping him on his right side, before vanishing right there.
...
MN 143 contains same verse passage as SN 2.20

vicine (8)

vicineyya (1)

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KN

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KN Ap.1, (paṭhamo bhāgo), 1. buddhavaggo, 3-1. sāriputtattherāpadānaṃ (KN 10.3), para. 382 ⇒
vicineyya vanaṃ sabbaṃ, byādhito parimuttiyā.

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KN Nett, sāsanapaṭṭhānaṃ, para. 365 ⇒
yoniso vicine dhammaṃ, evaṃ tattha visujjhati. 

KN Th, 10. dasakanipāto, 7. (apara)-gotamattheragāthā (KN 8.239), para. 20 ⇒
“sīlañca bāhusaccañca, dhammānaṃ pavicayo yathābhūtaṃ.